Tactical firearm having heat shielding properties and improved gas energized cartridge feeding

ABSTRACT

A tactical firearm having upper and lower receivers that are releasably connected. A cartridge gas energized bolt carrier assembly is moveable within the upper receiver and is provided with anti-tilt guidance with respect to a spring energized buffer mechanism, that is provided within a butt-stock of the lower receiver. The bolt carrier assembly moves a cartridge from a magazine and feeds the cartridge into the cartridge chamber of the barrel and returns the bolt carrier assembly to its closed and locked condition upon dissipation of the cartridge gas energizing force. The bolt carrier assembly is efficiently guided to prevent its misalignment during its rearward and forward auto-loading movement.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally to firearms and moreparticularly to semi or full automatic tactical firearms such as rifles.More particularly, the present invention concerns a tactical rifle thatmay be provided with semiautomatic and full automatic cartridge loading,firing and ejecting capability and is designed specifically for use of arelatively heavy bulleted cartridge such as the .308 which has a bulletdiameter of 7.62 mm. The present invention also concerns a tacticalfirearm having heat shielding properties to minimize the transfer ofheat from the barrel to the handguard such as during sustained rapidfire activities. Even more specifically the high accuracy tacticalfirearm of the present invention is designed with a continuous mountingrail having a desired angle of taper or cant to receive pivot actuatedlocking mounts of the type that is set forth in U.S. Pat. No. 7,272,904of Mark C. LaRue and to permit the mounts to be located virtuallyanywhere along the length of the continuous mounting rail.

2. Description of the Prior Art

During prolonged or sustained rapid fire activities the typically metalhandguards of tactical firearms often become heated to the extent thatsoldiers or law enforcement personnel or shooters in competitive matchesneed to wear gloves or use other protective devices to provide thermalisolation of the hands from the excessive heat of the handguard. Thisexcessive heating condition is exacerbated by the fact that thehandguards of most tactical rifles in use by the U.S. Military and otherrelated services are composed of a light-weight metal such as analuminum alloy, which is an efficient heat conducting material.Typically in military rifles a barrel nut is employed to secure thebarrel of the firearm to the receiver and the handguard defined a largeinternal barrel chamber, within which the barrel is mounted in freefloating relation. The rear end portion of the handguard is retained insupported assembly with the receiver and is in supported heattransferring relation with the outer periphery of the barrel nut. In theevent the barrel should become excessively heated, such as during rapidfire and sustained fire activities, the excessive heat build-up in theregion of the cartridge chamber of the barrel is typically transferredthrough the barrel mounting nut to the handguard. The handguard carrapidly become heated to the extent that it can burn and cause pain orinjury to the bare hands and arms of a firearm user. It is desirabletherefore to provide a novel tactical firearm incorporating the usualbarrel nut for releasable free floating barrel mounting but providingfor thermal isolation of the handguard from the barrel nut so that heatfrom the barrel will not be transferred in any substantial extent to thehandguard by heat transferring direct metal contact of the handguardwith the barrel or barrel support structure.

For highly accurate shooting activities, such as in the case of longrange marksmanship activities and for tactical sniper activities, it hasbeen well known for quite some time that well designed heavier riflebullets, such as bullets of 7.62 mm and greater have more consistentaccuracy in a wider variety of shooting conditions. While 6 mm bulletsare known to be quite accurate at short and medium ranges, such as up to300 meters for example, they are not typically considered particularlydesirable for precision long range shooting. At greater distances, suchas distances of 600 to 1000 meters or more the trajectory of smallerdiameter bullets tends to become adversely affected by lateral windconditions and wind resistance to a greater extent as compared withlarger diameter heavier bullets. During tactical conditions of firearmuse, however, a greater number of the smaller diameter and lighterweight cartridges can be more efficiently carried by the averagesoldier, which provides the advantage of greater firing rate duringtactical operations. It is desirable therefore to provide a noveltactical firearm that is designed for long range highly accurateshooting activity such as when the firearm is being used during longrange match shooting activities or is being used during sniperactivities by military or law enforcement personnel.

During the rapid fire use of virtually all firearms combustion of thepropellant of cartridges causes the development of considerable heatwhich causes heating of the barrel, especially in the region of thefiring chamber and causes heating of the receiver to some extent. If thefirearm is provided with a heat conducting handguard, which is typicalof tactical firearms, the handguard can become heated to the extent thatit can be painful to touch or hold it with the hands of the user. Thiscondition is especially prevalent when a tactical firearm is used duringrapid firing conditions. The M-16 and M-14 tactical rifles employ barrelnuts that are tightened to secure the barrel in removable relation withthe receiver of the firearm. The metal handguard is typically a twopiece unit that is composed of an aluminum alloy and is mounted incontact with and thus in heat transferring relation with the barrel nut.Forwardly of the barrel nut the barrel is for the most part freefloating and it often becomes heated during rapid fire conditions sothat it is too hot to touch. Excessive heat buildup of the barrel oftypical tactical firearms during rapid fire conditions is directlytransferred through the barrel nut to the handguard and causes excessiveheating of the handguard. It is desirable therefore to provide atactical firearm employing a barrel nut to releasably secure a barrel tothe receiver and to provide the firearm with a handguard that isisolated from direct heat transferring relation with the barrel andbarrel nut, thus permitting a user to easily hold the handguard of thefirearm even during conditions of rapid firing without encounteringconditions of excessive heat.

Tactical rifles, such as the M-16 and M-14 of the United States Armedforces, each incorporate a spring loaded bolt that is moved rearwardlyagainst a spring force acting on the bolt responsive to rifle firing bycartridge gas pressure that is communicated to the bolt from the barrelvia a barrel port and gas tube after a bullet moving within the barrelbore has cleared the barrel port. The rear portion of the bolt istypically unsupported as the bolt is moved rearwardly to engagement withthe buffer member by the force of cartridge gas pressure. After havingcontacted the buffer member the bolt enters the buffer chamber andcauses cushioning movement of a buffer member against the force of abuffer spring. At times, especially during conditions of rapid fire, therear portion of the bolt can become misaligned or tilted with respect tothe opening of the buffer receptacle during its rearward movement. Thismisalignment or tilting of the bolt mechanism can retard bolt movementand/or cause failure of the cartridge case extractor of the boltmechanism to properly extract a spent cartridge case from the firingchamber and eject it from the ejector opening of the receiver of thefirearm. When this undesired condition occurs the spent cartridge case,being improperly extracted and ejected, can become jammed or otherwiseinterfere with bolt movement as the bolt is subsequently moved forwardlyby the force of the buffer spring. This condition will cause failure ofthe bolt mechanism to properly feed a fresh cartridge from the magazineof the firearm and can require time consuming manual adjustment of thecartridge feeding mechanism of the firearm to restore it to properoperating condition. Most importantly, this cartridge extracting,ejecting and feeding can jeopardize the safety of personnel if it shouldoccur during tactical conditions. It is desirable therefore to provide anovel tactical firearm mechanism incorporating an anti-tiltcharacteristic that ensure precise and efficient guiding of the boltcarrier and bolt mechanism during all stages of its rearward gasenergized movement and its forward spring energized movement duringfirearm use to thus ensure efficient cartridge case auto-ejection andfresh cartridge feeding during all stages of mechanical activity as thefirearm is operated either during conditions of slow fire or sustainedrapid fire.

M-16 and M-14 tactical rifles and similar rifles, such as the AR-15semi-automatic rifle, typically incorporate a handguard that is securedto the receiver of the firearm by means of a handguard retainer nut thatis typically tightened manually. At times the handguard retainer nut islocked in place after it has been tightened. While this manner ofreceiver/handguard attachment is typically desirable for lightweight,small bore tactical rifles and permits disassembly of the handguard fromthe receiver, even in field conditions, for a heavier bore and highlyaccurate long range rifle, the stability and structural integrity of themechanism that joins the handguard to the receiver mechanism isconsidered paramount. The accuracy of the rifle can be adverselyaffected if the receiver/handguard connection results in a somewhatflexible assembly. Accordingly, it is considered desirable to provide afirearm having a connection joint between the receiver and the handguardthat has enhanced structural integrity thus resulting in a quite rigidfirearm structure which materially enhances the accuracy of the firearm.

Many tactical rifles are provided with sight mounting rails, such as thePicatinny rail, for example, with a section of a sight mounting raillocated on the receiver and with another section of sight mounting raillocated on the handguard. Lateral and bottom mounting rails of similardesign are typically mounted on the handguard so that variousaccessories, such as white or ultraviolet lights can be mounted to thefirearm to aid firearm sighting by the user during various conditions oflight. Since a handguard is typically mounted to the receiver be meansof a handguard retainer nut and nut locking mechanism, it is notpractical to mount sighting devices on the rail of the handguard sincethe handguard is typically a free floating device and its position canvary with respect to the receiver and barrel of the firearm. Rather,sighting devices are typically mounted to the rail of the receiver sincethe receiver and barrel are secured in immovable assembly. It isdesirable, however, to provide a firearm with a sight mounting railsystem that is arranged to permit location of a sighting device at anydesired location along the combined length of the receiver andhandguard. It is also desirable to provide a sight mounting rail systemthat permits two or more sighting devices to be mounted in series alongthe combined length of the receiver and handguard and also permits amechanical sighting device to be mounted to the rear portion receiverand to be used for sighting when the optical sighting devices have beenremoved from the mounting rail.

SUMMARY OF THE INVENTION

It is a principal feature of the present invention to provide a noveltactical firearm having a handguard that is mounted to the receiver insuch manner that the handguard is substantially isolated from the barreland barrel retainer nut of the firearm from the standpoint of thermalconductivity, thus preventing excessive heating of the handguard evenduring conditions of sustained rapid fire so that the firearm can beefficiently utilized by personnel.

It is another feature of the present invention to provide a noveltactical firearm mechanism that permits the barrel of the firearm to besubstantially free floating within and substantially along the entirelength of the handguard and to maintain the handguard in spaced andthermally isolated relation with the barrel to protect the user from theexcessive heat that typically builds up during rapid firing conditions.

It is also a feature of the present invention to provide a noveltactical firearm mechanism that provides the reciprocating bolt carrierand bolt of a semi-automatic or full automatic tactical rifle withefficient guiding during the entirety of its rearward and forwardauto-loading movement, thus preventing misalignment or tilting of thebolt during its rearward movement;

It is another feature of the present invention to provide a novelauto-loading tactical firearm that ensures proper cartridge caseextraction and ejection during rearward movement of the bolt carrier andbolt thereof and facilitating efficient cartridge loading during forwardmovement and also minimizing the potential for cartridge mis-feeding.

It is an even further feature of the present invention to provide anovel tactical firearm having a handguard and receiver that are joinedin a manner that lends significant structural integrity and rigidity tothe assembly of the receiver and handguard which contributessignificantly to the accuracy of the firearm.

It is another feature of the present invention to provide a noveltactical firearm that is designed with an elongated sight mounting railsuch as a Picatinny rail and wherein the rail extends substantially theentire length of the combined receiver and handguard and is providedwith a predetermined angle of tilt or cant to facilitate the mounting ofa sight at any selected location along the length of the mounting rail.The elongate sight mounting rail is also designed to facilitate themounting of a conventional mechanical sighting device, typicallyreferred to as an “iron sight” for use of the firearm when opticalsights are not present on the sight mounting rail.

It is another feature of the present invention to provide a noveltactical firearm having a sight mounting rail system that permits two ormore sighting devices to be mounted in series along the combined lengthof the receiver and handguard.

Briefly, the various objects and features of the present invention arerealized by providing a tactical firearm having a receiver and handguardthat are connected by mounting flanges that are secured in surface tosurface engagement by a plurality of retainers to provide a receiver andhandguard assembly of enhanced structural integrity. A single uppersight mounting rail having a length substantially equal to the combinedlength of the receiver and handguard of the tactical rifle is fixed toboth the receiver and handguard. The single upper mounting rail furtherenhances the structural integrity of the flange connection of thereceiver and handguard and has an angular cant of a desired angle thatpermits one or more sighting devices to be mounted at any suitablelocation along the length of the single upper mounting rail. A desiredangular cant of 20 minutes of angle has been found desirable for atactical rifle representing a preferred embodiment of the presentinvention. However, it is to be understood that the present invention isnot intended to be limited by a cant of 20 minutes of angle, it beingwithin the spirit and scope of the present invention to provide thesingle sight mounting rail with any other desired angle of cant. Thesight mounting rail is provided with a desired exterior profile, such asthe cross-sectional profile of a Picatinny rail for example, to permitlever actuated cam energized rail clamping mechanisms to be releasablyattached thereto so that sighting devices can be removed and replacedwithout loss of zero. A preferred lever actuated cam energized railclamping mechanism for this purpose is constructed according to theteachings of U.S. Pat. No. 7,272,904 of Mark C. LaRue. Additionally, therear portion of the single mounting rail defines a rail seat for a rearmechanical sighting device, typically referred to as an “iron sight”which is typically adjustable for windage and elevation and can be usedfor mechanical sighting when the optical, laser or other sightingdevices have been removed from the mounting rail.

Bolt or bolt carrier tilting takes place because the rear portion of aconventional bolt mechanism is typically unsupported during its gasenergized rearward movement responsive to the sudden rearward movementthat occurs as a cartridge is fired. This tilting or misalignment causesthe bolt mechanism to come into contact with structure surrounding theinlet opening of a buffer mechanism, causing jarring or jamming of thebolt mechanism so that the cartridge case of the cartridge that has beenfired will often fail to be properly extracted and ejected. In responseto the force of a buffer spring that has been loaded during rearwardmovement of the bolt mechanism, as the bolt mechanism begins to be movedforwardly the improperly extracted and ejected cartridge case will ofteninterfere with the capability of the bolt to remove a fresh cartridgefrom the cartridge magazine and charge the fresh cartridge into thecartridge chamber of the barrel and cause locking movement of the bolt.This condition typically results in a jam that prevents furtheroperation of the firearm until the jam has been cleared.

According to the principles of the present invention firearm jamming dueto bolt tilting during firing is largely eliminated by ensuring that thebolt carrier and bolt mechanism are guided and prevented from becomingtilted during all phases of bolt and bolt carrier movement. A bufferhousing is located within a portion of the buttstock of the tacticalrifle and contains a tubular buffer member that is urged forwardlytoward a stop member by a buffer spring. Within the receiver of thefirearm is provided a bolt and bolt carrier assembly that are movedrearwardly by cartridge gas pressure and are moved forwardly by theforce of a compressed buffer spring. The bolt carrier has a rear endportion that is positioned in guided relation with a guide memberlocated within the inlet opening of the buffer housing. When the boltcarrier and bolt are in closed and locked relation within the receiverthe rear end portion of the bolt carrier member is in engagement withthe guide member. This causes the bolt carrier to be guided during allphases of its forward and rearward movement by the internal guide memberwithin the inlet portion of the buffer housing so that the bolt carriermember cannot become tilted or in any way misaligned with respect to theinlet opening of the buffer housing. This anti-tilt bolt guidingstructure is a positive co-axial bolt carrier alignment system thatensures accurate guided positioning of the bolt assembly at all stagesof its travel. The bolt tilt problem that typically plagues thecartridge case ejection and cartridge feeding activity of many tacticalfirearms is overcome by the alignment and guiding activity of thepositive co-axial bolt carrier alignment system of the tactical firearmof the present invention. Since no bolt tilting can occur duringrearward gas energized movement of the bolt mechanism the cartridge caseextraction and fresh cartridge feeding activity of the tactical firearm,the bolt alignment and guiding system ensures against cartridge jammingthat can result from bolt tilting.

The barrel of the tactical firearm is mounted in immovable butreleasable relation with respect to the receiver by a barrel nut that isin threaded engagement with a threaded barrel retainer extension of thereceiver. When tightened by a barrel nut wrench the barrel nut causesforcible engagement of an annular rib or flange of the barrel with thecircular end surface of the barrel retainer extension. The handguard iscomposed of a metal such as an aluminum alloy that is chosen for itslight weight characteristics. Unfortunately this light weight metal isalso capable of efficiently conducting heat. The handguard defines acentral chamber within which the barrel is free floating. The forwardend of the handguard is positioned about and in spaced and thermallyisolating relation with the barrel nut so that the space between thehandguard and the barrel nut prevents rapid transfer of heat from thebarrel through the barrel nut to the handguard. Since the barrel nut isquickly heated by heat transfer from the barrel due to the firing ofcartridges within the cartridge chamber of the barrel, the spacedrelation of the handguard about the barrel nut prevents the handguardfrom being excessive heat such as would occur if the handguard were inmetal to metal thermal transferring contact with the barrel. This heatshielding or thermal isolating feature permits a user of the firearm toefficiently grip the handguard and handle the firearm, even duringconditions of sustained rapid fire, without experiencing any discomfortthat might otherwise be caused by touching an excessively heated firearmcomponent.

The lower receiver portion of the tactical firearm of the presentinvention is provided with a magazine receptacle within which isreceived a replaceable spring loaded magazine containing a number ofcartridges that are positioned to be individually moved from themagazine into the cartridge chamber of the barrel as the bolt mechanismis moved from its rearmost position forwardly by the force of the bufferspring. Ease of cartridge movement from the magazine occurs due to thepresence of internal guide bosses that establish minimal metal to metalcontact with the case of the leading cartridge and thus minimize thefrictional resistance to cartridge movement as the moving bolt mechanismis moved forwardly by the force of the buffer spring.

BRIEF DESCRIPTION OF THE DRAWINGS

So that the manner in which the above recited features, advantages andobjects of the present invention are attained and can be understood indetail, a more particular description of the invention, brieflysummarized above, may be had by reference to the preferred embodimentthereof which is illustrated in the appended drawings, which drawingsare incorporated as a part hereof.

It is to be noted however, that the appended drawings illustrate only atypical embodiment of this invention and are therefore not to beconsidered limiting of its scope, for the invention may admit to otherequally effective embodiments.

In the Drawings:

FIG. 1 is an elevational view showing a tactical firearm embodying theprinciples of the present invention;

FIG. 2 is a top plan view showing the flange mounted upper receiver andhandguard of the firearm of FIG. 1 and further showing the elongateone-piece sight mounting rail thereof being mounted to the upperreceiver and handguard of the firearm;

FIG. 3 is a sectional view taken along line 3-3 of FIG. 2 and showingfurther details of the firearm mechanism of FIGS. 1 and 2;

FIG. 4 is a side elevation view showing the flange mounted upperreceiver and handguard of the firearm of FIG. 1 and also showing therelation of the one-piece sight mounting rail to the upper receiver andhandguard;

FIG. 5 is an isometric illustration showing the mounting flange of theupper receiver in detail and further showing mounting of the barrel ofthe firearm to the upper receiver;

FIG. 6 is another isometric illustration showing the mounting flange ofthe upper receiver from another point of view and also showing thebarrel and barrel mount nut of the firearm;

FIG. 7 is a fragmentary sectional view showing the flanged mounting ofthe upper receiver and handguard illustrating the thermal isolation ofthe handguard from the barrel retainer nut of the firearm; and

FIG. 8 is a partial side elevational view showing portions of the upperreceiver, lower receiver and buttstock and illustrating the boltanti-tilt mechanism of the firearm.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENT

Referring now to the drawings and first to the elevational view of FIG.1, there is shown a tactical firearm generally at 10 embodying theprinciples of the present invention. The firearm 10, is preferably inthe form of a tactical rifle of relatively heavy bore, such as beingchambered for the 7.62 mm United States Military cartridge, alsoreferred to as the .308 caliber rifle cartridge. However, it should beborne in mind that the present invention is applicable to firearms ofboth lighter and heavier bore without departing from the spirit andscope of the invention. For purposes of simplicity, though the scope ofthis invention encompasses a wide range of firearm devices, theinvention is referred to herein as a tactical rifle.

The tactical rifle 10 incorporates an upper receiver 12 to which a lowerreceiver 14 is pivotally mounted by means of a pivot pin 16 whichextends through corresponding pivot openings of the lower receiver 14and a pivot opening 18 of a downwardly extending pivot projection 20 ofthe upper receiver 12. The pivot pin 16 permits the relative pivotalmovement of the upper and lower receivers so that the breach of thefirearm can be exposed for cleaning, servicing or for field maintenanceas needed. The lower receiver 14 is provided with a handgrip 22, atrigger guard 24 and a magazine receptacle 26. A cartridge containingmagazine 28 is received by the magazine receptacle and is secured inplace by a magazine catch. The magazine maintains the first of a numberof cartridges in position to be fed from the magazine and into thefiring chamber of the rifle barrel as the bolt mechanism of the rifle ismoved forwardly. The closed and locked position of the lower receiverwith respect to the upper receiver is shown in FIG. 1 and is achieved bya locking pin 30 which is moveable to a locking position in engagementwithin the locking opening 32 of a locking lug 34 that projectsdownwardly from the rear portion of the upper receiver 12 as shown inFIG. 2.

It is desirable from the standpoint of the present invention to providethe tactical rifle with a receiver and handguard assembly havingconsiderable structural integrity so that the handguard and receiver areimmovable one relative to the other. This feature is important topromote the efficient long range firing characteristics of the rifle andto permit the location of sighting devices at any selected locationalong the combined length of the receiver and handguard. This feature isaccomplished by a first mounting flange 36 which is located at the frontend of the upper receiver 12 and by a second mounting flange 38 that isprovided at the rear end of a handguard member 40. The mounting flanges36 and 38 each define planar surfaces such as shown at 42 in FIGS. 5 and6 which are disposed in surface to surface engagement when the handguardis secured in tight assembly with the upper receiver. The secondmounting flange 38 of the handguard is provided with a plurality ofinternally threaded retainer openings which are in registry with a likenumber of retainer openings 44 of the mounting flange 36 of the upperreceiver 12. Fastener members, such as Allen screws or any othersuitable fasteners, are threaded into place and secure the first andsecond mounting flanges 36 and 38 in immovable assembly. Alternatively,if desired a plurality of bolt and nut assemblies may be employed tosecure the mounting flanges to one another. After the mounting flangeshave been secured in this manner the resulting elongated structure ofthe upper receiver and handguard constitute an elongated essentiallyrigid unitary rifle component having a length that is essentiallydefined by the combined length of the upper receiver 12 and handguard40.

As is evident in the sectional view of FIG. 3 and the elevation view ofFIG. 4 the upper receiver 12 defines an upper generally planar railmounting surface 46 and the upper portion of the handguard 40 defines anupper generally planar rail mounting surface 48. When the handguard issecured to the upper receiver 12 by the flange assembly as discussedabove, the substantially planar surfaces 46 and 48 are disposed inco-planar relation, thus essentially defining an elongate rail mountingsurface having a length that is substantially equal to the combinedlength of the upper receiver and handguard. An elongate one piece sightmounting rail 50, which may be designed with a cross-sectional geometryin the form of a conventional Picatinny rail, is secured with its lowersurface 52 in surface to surface supported engagement with an elongaterail mounting surface 47 that is defined by the co-planar surfaces 46and 48 of the receiver and handguard. A plurality of retainer members 49such as Allen screws extend through openings of the elongate one piecesight mounting rail and are threaded into threaded openings of the upperreceiver and handguard. The elongate one piece sight mounting rail 50 isof sufficient length to extend substantially the entirety of the flangesecured upper receiver 12 and handguard 40 and has sufficient structuralintegrity to significantly enhance the structural integrity of theassembled upper receiver and handguard unit of the tactical rifle. Thisfeature provides the tactical firearm with considerable strength andresistance to bending or other mechanical distortion, thus enhancing theaccuracy of the rifle and making it suitable for long range highlyaccurate shooting. The elongate one piece sight mounting rail 50 has aplurality of evenly spaced lands 53 and sight location grooves 55 alongthe length thereof, with the sight location grooves each defining groovebottom surfaces that are preferably located in a common plane having thetaper or cant of the rail, though the bottom surfaces of the grooves maybe otherwise located without departing from the spirit and scope of thepresent invention.

As is mentioned above, it is desirable to provide for mounting of one ormore sighting devices at any selected location along the combined lengthof the upper receiver and handguard. This feature is accomplished by theone-piece sight mounting rail 50. A single optical sighting device 54 isshown to be mounted to the single sight mounting rail by means of leveractuated releasable clamp mechanisms 56 that are constructed accordingto the principles set forth is U.S. Pat. No. 7,272,904 of Mark C. LaRue,which patent is incorporated herein by reference for all purposes. It isnot intended however to restrict the use of the one-piece sight mountingrail to sight mounts having releasable lever actuated clamp mechanismssince any suitable sight mounting devices may be employed for sightmounting without departing from the spirit and scope of the presentinvention. The one-piece sight mounting rail 50 is gradually taperedfrom end to end so that the rear end thereof is of greater thicknessdimension as compared with the thickness dimension of the front endportion. This feature is evidenced by the relative spacing of front andrear extended thickness lines shown at t₁ and t₂ in FIG. 3. Though anydesired taper of the one-piece sight mounting rail may be employed, forpurposes of the preferred embodiment of the present invention the taperor cant that is employed is 20 minutes of angle. Thus, the one-piecesight mounting rail 50 defines an elongate sight mounting structure thatis inclined at 20 minutes of angle with respect to the center-line ofthe bore of the barrel. This feature, together with the considerableunbroken length of the one-piece sight mounting rail permits themounting of optical sighting devices at any desired location along thecombined length of the upper receiver 12 and handguard 40 of thefirearm. A rear portion of the one-piece sight mounting rail defines agenerally planar surface 45 having a desired elevation for properlypositioning a mechanical sighting device, typically referred to as an“iron sight” to enable manual sighting of the firearm when the optical,laser or other sighting devices have been removed from the rail. Themechanical sight mount surface 45 may have an elevation that is lower orhigher as compared with the elevation of the lands 53 so that an ironsight mounted thereto will have a proper elevation for manual sightingwith respect to a conventional blade type front sight (not shown). Themechanical sight mount seat or platform 45 defines sight location keyslot 51, shown in FIGS. 2 and 3, within which the location key of theiron sight mechanism is received. The mechanical sight mount seat orplatform 45 has an elevation that is substantially equal to theelevation of the positioning groove bottom surfaces of the elongatesight mounting rail 50. Thus, when the optical and other sightingdevices have been removed from the sight mounting rail 50 a mechanicalor iron sighting device may be mounted to the mechanical sight mountseat or platform 45 and may be employed for manual sighting of thefirearm.

As mentioned above, when auto-loading tactical firearms are used duringrapid fire, especially sustained rapid fire the heat that builds up inthe barrel 64, especially in the region of the cartridge chamber 66 andbarrel retainer nut is typically conducted to the handguard due to thecontact of the handguard with the barrel retainer nut. Especially sincethe handguard is typically composed of a lightweight metal such as analuminum alloy, the handguard can rapidly become excessively heated sothat it can be painful to grip with the bare hands of the user. Oftentimes a user of this type of firearm will wear thermal insulating glovesor use a thick cloth or some other protective device to ensure that theuser can continue to grip the handguard even when the handguard hasbecome too hot to manually handle. To overcome this undesirablecondition the rigid connection that is established by the retainedmounting flanges 36 and 38 positions the inside surface 60 of thehandguard in spaced and thermally isolated relation with the outerperiphery 62 of the barrel nut 58 as shown in FIG. 7. The clearance orannular gap that separates the outer periphery 62 of the barrel nut fromthe inner surface 60 of the handguard serves as thermal isolation whichminimizes heat transfer to the handguard 40. Thus, the handguard will beprotected from excessive heating so that a user can comfortably handlethe firearm during all conditions of firing.

As mentioned above the rear portion of the bolt and bolt carrierassembly of a tactical rifle is typically unsupported during itsrearward movement against the buffer and buffer spring that are locatedin a buffer receptacle within the buttstock of the firearm. For thisreason the bolt carrier can be shifted laterally, typically downwardlydue to its weight, and can become tilted as it proceeds rearwardly inresponse to the gas pressure of cartridge firing. When bolt carriertilting occurs, the rear end portion of the bolt carrier can contact thebuttstock structure or a buffer retainer, thus at least partiallystalling the rearward movement of the bolt carrier and preventing itfrom smoothly entering into the buffer chamber and displacing the buffermember against the force of the buffer spring. This bolt carrier tiltingcondition often causes failure of the extractor of the bolt mechanism tomove a cartridge case rearwardly until it engages the ejector and isejected laterally from the ejection opening of the upper receiver. Whenthis bolt carrier tilting condition occurs an empty cartridge case canremain within the cartridge chamber of the barrel or it can be onlypartially extracted from the cartridge chamber. The cartridge case canbe improperly positioned within the receiver so that it fouls the boltand bolt carrier assembly and causes a jam, thus preventing the properfeeding of a fresh cartridge from the magazine by the buffer springenergized forwardly moving bolt mechanism. This undesirable bolt tiltingcondition is overcome according to the principles of the presentinvention by ensuring that the rear portion of the bolt carrier ispositively guided during all phases of its rearward recoil movement andits forward cartridge charging movement.

A buttstock 66 is mounted to the lower receiver 14 as shown in FIG. 8and has a buffer tube 68 located therein. A tubular buffer member 70 ismovable within the buffer tube and is urged forwardly by a buffer spring72. The buffer member 70 defines a substantially planar forward endsurface or face 74 that is positioned for engagement by the rear endportion of a bolt carrier member 76 having a bolt carrier 76 and a boltmember 77 that is moved rearwardly within the upper receiver 12responsive to the energy of cartridge gas pressure. Cartridge gaspressure is supplied to a bolt actuator mechanism 78 having drivingrelation with the bolt mechanism by a gas tube 80 that is incommunication with a barrel port via a barrel port block 82. The barrelport block 82 is positioned within the forward portion of the handguardas shown in FIG. 3. The barrel port block 82 may permit cartridge gaspressure communication with the gas tube 80 via a single port of thebarrel. Preferably, however, the barrel port block is selectorcontrolled and is capable of permitting selective communication of asingle barrel port or two or more barrel ports with the gas tubeaccording to the features set forth in U.S. Provisional PatentApplication No. 61/279,817, filed on Oct. 26, 2009 by Mark C. LaRue.

The rear end portion of the bolt carrier member 76 is supported andguided by an annular guide surface 84 and is thus prevented frombecoming tilted as the bolt is driven rearwardly in response to thefiring of a cartridge. When the bolt carrier member 76 is at its forwardmost location within the upper receiver 12 the rear end portion of thebolt mechanism is located within the annular guide surface 84 and is inengagement with the planar front end surface 74 of the buffer member 70.The rear end portion of the bolt carrier member 76, when the boltmechanism is closed and locked, is positioned in guided relation withthe internal guide surface 84 and causes slight compression of thebuffer spring 72. Thus, when a cartridge is fired and gas pressureactuates the bolt carrier and bolt mechanism rearwardly, the boltcarrier member is positioned and guided at all times by the internalguide surface. The rear end portion of the bolt carrier member ispositively oriented and guided at all times and cannot be tiltedlaterally as the result of the sudden application of rearward force thatis applied thereto when a cartridge is fired. The bolt carrier member 76can only move linearly as it is forced into the buffer chamber anddisplaces the buffer member against the force of the buffer spring. Thebolt mechanism, therefore, is properly positioned at all times by thisanti-tilt control and thus cannot become tilted during its rearwardmovement. The cartridge case extractor of the bolt member 77 will remainproperly positioned at all times to efficiently extract the cartridgecase of a fired cartridge and the ejector of the bolt assembly willcause ejection of the spent cartridge case from the ejection opening 86of the upper receiver 12.

In view of the foregoing it is evident that the present invention is onewell adapted to attain all of the objects and features hereinabove setforth, together with other objects and features which are inherent inthe apparatus disclosed herein.

As will be readily apparent to those skilled in the art, the presentinvention may easily be produced in other specific forms withoutdeparting from its spirit or essential characteristics. The presentembodiment is, therefore, to be considered as merely illustrative andnot restrictive, the scope of the invention being indicated by theclaims rather than the foregoing description, and all changes which comewithin the meaning and range of equivalence of the claims are thereforeintended to be embraced therein.

I claim:
 1. A tactical firearm, comprising: a receiver member defining afirst mounting flange and having a first rail mounting surface; ahandguard member defining a second mounting flange being secured in faceto face relation with said first mounting flange; and flange fastenermembers securing said first and second mounting flanges in releasablefixed relation with one another.
 2. The tactical firearm of claim 1,comprising: said receiver member defining a first rail mounting surfaceand said handguard member defining a second rail mounting surface beingdisposed in co-planar relation with said first rail mounting surface; aone-piece elongate sight mounting rail extending substantially along thecombined length of said receiver member and said handguard member anddefining a mounting surface having face to face relation with said firstand second rail mounting surfaces, said one-piece elongate sightmounting rail having a cross-sectional mount geometry for receivingclamp type sight mount devices in releasable clamped relation therewith;and rail fastener members securing said one-piece elongate sightmounting rail to said receiver and said handguard.
 3. The tacticalfirearm of claim 2, comprising: said receiver having a rear end portionand a front end portion; said handguard having a rear end portion and afront end portion; and said one-piece elongate sight mounting railhaving a rear end located at said rear portion of said receiver and afront end located at said front portion of said handguard and beingvertically tapered from a predetermined dimension at said rear end to adimension less than said predetermined dimension at said front endthereof.
 4. The tactical firearm of claim 1, comprising: a barrel memberextending through said handguard member and being mounted to saidreceiver member; a barrel retainer nut being threaded to said receivermember and securing said barrel member in oriented and substantiallyimmovable relation with said receiver member; and said handguarddefining an inner surface disposed in spaced relation with said barrelmember and said barrel nut and being thermally isolated from metalconducted transfer of heat from said barrel member and said barrelretainer nut to said handguard.
 5. The tactical firearm of claim 1,comprising: a one-piece elongate sight mounting rail being mounted tosaid receiver and said handguard and having a length substantially equalto the combined length of said receiver and said handguard; and saidone-piece elongate sight mounting rail being tapered along a majorportion of the length thereof and defining a predetermined angle of cantfor location of sighting devices at any selected position along thelength thereof.
 6. The tactical firearm of claim 5, comprising: saidone-piece elongate sight mounting rail defining a rear portion locatedat a rear portion of said receiver and a front portion located at afront portion of said handguard having a greater vertical thickness atsaid rear portion as compared with the vertical thickness at said frontportion thereof.
 7. The tactical firearm of claim 5, comprising: saidone-piece elongate sight mounting rail defining a single mechanicalsight mount located at said rear portion thereof, said single mechanicalsight mount having an elevation permitting manual sighting of saidfirearm when optical sighting devices have been removed from saidone-piece elongate sight mounting rail.
 8. The tactical firearm of claim5, comprising: said one-piece elongate sight mounting rail having aplurality of equally spaced lands and sight positioning grooves locatedsubstantially along the length thereof; and said one-piece elongatesight mounting rail defining a single mechanical sight mount structurebeing located at the rear portion of said one-piece elongate sightmounting rail and having a sight orienting surface and mechanical sightpositioning groove for attachment of a mechanical sighting devicethereon.
 9. The tactical firearm of claim 1, comprising: said receivermember having a bolt chamber located therein; a bolt carrier havingreciprocating movement within said bolt chamber and having a bolt memberlocated therein; a buttstock being mounted to said receiver member andhaving a buffer housing therein defining a buffer stop; a spring urgedbuffer member being moveable within said buffer housing and havingreciprocating movement limited by said buffer stop; and said boltcarrier having a portion thereof located within said buffer housing andin contact with said buffer member and having guided relation with saidbuffer stop and preventing tilting of said bolt carrier during rearwardmovement thereof.
 10. The tactical firearm of claim 1, comprising: saidreceiver member having a bolt chamber located therein; a bolt carrierhaving reciprocating cartridge autoloading movement within said boltchamber and having a bolt member located therein, said bolt carrier andbolt member being moved rearwardly within said bolt chamber by cartridgegas pressure resulting from firing of said tactical firearm; a bufferhousing having a bolt carrier guide member; a spring urged buffer memberhaving rearward movement within said buffer housing responsive torearward movement of said bolt carrier and having forward movementwithin said buffer housing by said spring; and said bolt carrier havinga portion thereof in guided relation with said carrier guide member andbeing guided during rearward and forward reciprocating movement of saidbolt carrier and bolt.
 11. The tactical firearm of claim 1, comprising:said receiver member being defined by an upper receiver defining a boltchamber and a lower receiver having a buttstock and defining a bufferhousing; a spring urged buffer member being moveable within said bufferchamber; and a bolt carrier having a bolt member therein and having arear end portion thereof in constant engagement with said buffer memberand in anti-tilt guided relation with said buffer housing, upon rearwardmovement of said bolt carrier responsive to cartridge firing said boltcarrier causing rearward cushioning movement of said spring urged buffermember and being guided by said buffer housing to prevent tiltingthereof during both rearward cartridge firing movement and forwardspring urged movement.
 12. A tactical firearm, comprising: a receivermember defining a first mounting flange and having a first rail mountingsurface; a handguard member defining a second mounting flange and havinga second rail mounting surface disposed in co-planar relation with saidfirst rail mounting surface, said first and second mounting flangesbeing mounted in face to face relation and defining a firearm unit ofrigid and structurally enhanced character; flange fastener memberssecuring said first and second mounting flanges in releasable fixedrelation with one another; a one-piece elongate sight mounting railextending substantially along the combined length of said receivermember and said handguard member and defining a substantially planarmounting surface having face to face relation with said first and secondrail mounting surfaces, said one-piece elongate sight mounting railhaving a cross-sectional mount geometry for receiving clamp type sightmount devices in releasable clamped relation therewith; and railfastener members securing said one-piece elongate sight mounting rail infixed relation with said receiver and said handguard and furtherenhancing the rigidity and structurally enhanced character of saidfirearm unit.
 13. The tactical firearm of claim 12, comprising: saidreceiver having a rear end portion and a front end portion; saidhandguard having a rear end portion and a front end portion; and saidone-piece elongate sight mounting rail having a rear end located at saidrear portion of said receiver and a front end located at said frontportion of said handguard and being vertically tapered from apredetermined dimension at said rear end to a dimension less than saidpredetermined dimension at said front end thereof.
 14. The tacticalfirearm of claim 12, comprising: a barrel member extending through andin free-floating relation within said handguard member and havingcartridge receiving relation with said receiver member; a barrelretainer nut being threaded to said receiver member and securing a rearend portion of said barrel member in oriented and substantiallyimmovable relation with said receiver member; and said handguarddefining an inner surface disposed in spaced relation with said barrelmember and said barrel nut and being thermally isolated from metalconducted transfer of heat from said barrel member and said barrelretainer nut to said handguard.
 15. The tactical firearm of claim 12,comprising: a one-piece elongate sight mounting rail being mounted tosaid receiver and said handguard and having a length substantially equalto the combined length of said receiver and said handguard; and saidone-piece elongate sight mounting rail defining a rear portion locatedat a rear portion of said receiver and a front portion located at afront portion of said handguard having a greater vertical thickness atsaid rear portion as compared with the vertical thickness at said frontportion thereof and being tapered along the length thereof and defininga predetermined angle of cant for location of sighting devices at anyselected position along the length thereof.
 16. The tactical firearm ofclaim 15, comprising: said one-piece elongate sight mounting raildefining a single mechanical sight mount located at said rear portionthereof, said single mechanical sight mount having an elevationpermitting manual sighting of said firearm when optical sighting deviceshave been removed from said one-piece elongate sight mounting rail; aplurality of equally spaced lands and sight positioning grooves beinglocated substantially along the length of said one-piece elongate sightmounting rail having; and a single mechanical sight mount structurebeing located at the rear portion of said one-piece elongate sightmounting rail and having a sight orienting surface and mechanical sightpositioning groove for attachment of a mechanical sighting devicethereon.
 17. The tactical firearm of claim 12, comprising: said receivermember having a bolt chamber located therein; a bolt carrier havingreciprocating movement within said bolt chamber and having a bolt memberlocated therein; a buttstock being mounted to said receiver member andhaving a buffer housing therein defining a buffer stop; a spring urgedbuffer member being moveable within said buffer housing and havingreciprocating movement limited by said buffer stop; and said boltcarrier having a portion thereof located within said buffer housing andin contact with said buffer member and having guided relation with saidbuffer stop and preventing tilting of said bolt carrier during rearwardmovement thereof.
 18. The tactical firearm of claim 12, comprising: saidreceiver member having a bolt chamber located therein; a bolt carrierhaving reciprocating autoloading movement within said bolt chamber andhaving a bolt member located therein, said bolt carrier and bolt memberbeing moved rearwardly within said bolt chamber by cartridge gaspressure resulting from firing of said tactical firearm; a bufferhousing having a bolt carrier guide member; a spring urged buffer memberhaving rearward movement within said buffer housing responsive torearward movement of said bolt carrier and having forward movementwithin said buffer housing by said spring; and said bolt carrier havinga portion thereof in guided relation with said carrier guide member andbeing guided during rearward and forward reciprocating movement of saidbolt carrier and bolt.
 19. The tactical firearm of claim 12, comprising:said receiver member being defined by an upper receiver defining a boltchamber and a lower receiver having a buttstock and defining a bufferhousing; a spring urged buffer member being moveable within said bufferchamber; and a bolt carrier having a bolt member therein and having arear end portion thereof in constant engagement with said buffer memberand in anti-tilt guided relation with said buffer housing, upon rearwardmovement of said bolt carrier responsive to cartridge firing said boltcarrier causing rearward cushioning movement of said spring urged buffermember and being guided by said buffer housing to prevent tiltingthereof during both rearward cartridge firing movement and forwardspring urged movement.